Hydrogen storage in a microporous metal-organic framework with exposed Mn2+ coordination sites

Use of the tritopic bridging ligand 1,3,5-benzenetristetrazolate (BTT3-) enables formation of [Mn(DMF)(6)](3)[(Mn4Cl)(3)(BTT)(8)(H2O)(12)](2)center dot 42DMF center dot 11H(2)O center dot 20CH(3)OH, featuring a porous metal-organic framework with a previously unknown cubic topology. Crystals of the compound remain intact upon desolvation and show a total H-2 uptake of 6.9 wt % at 77 K and 90 bar, which at 60 g H-2/L provides a storage density 85% of that of liquid hydrogen. The material exhibits a maximum isosteric heat of adsorption of 10.1 kJ/mol, the highest yet observed for a metal-organic framework. Neutron powder diffraction data demonstrate that this is directly related to H-2 binding at coordinatively unsaturated Mn2+ centers within the framework.